Vertical cavity surface emitting laser

Abstract

A Vertical cavity surface emitting laser (VCSEL) capable of providing high output of fundamental transverse mode while preventing oscillation of high-order transverse mode is provided. The VCSEL includes a semiconductor layer including an active layer and a current confinement layer, and a transverse mode adjustment section formed on the semiconductor layer. The current confinement layer has a current injection region and a current confinement region. The transverse mode adjustment section has a high reflectance area and a low reflectance area. The high reflectance area is formed in a region including a first opposed region opposing to a center point of the current injection region. A center point of the high reflectance area is arranged in a region different from the first opposed region. The low reflectance area is formed in a region where the high reflectance area is not formed, in an opposed region opposing to the current injection region.

Description

CROSS REFERENCES TO RELATED APPLICATIONS

S≥0.1×W₂   Formula 2

Further, where the reflectance in the case where the foregoing adjustment layers are not provided in the aperture of the upper electrode 19 is R₃, each refractive index is preferably adjusted to satisfy the following Formula 3. Thereby, high-order transverse mode oscillation is able to be selectively prevented without decreasing the light output of the fundamental transverse mode.
R₁≥R₃≥R₂   Formula 3

The laser diode 1 according to this embodiment may be manufactured, for example, as follows.

FIGS. 6A and 6B to FIGS. 8A and 8B illustrate the manufacturing method in the order of steps. FIGS. 6A and 6B to FIGS. 8A and 8B respectively illustrate a structure of a cross section taken along the same direction as the direction of arrows A-A of FIG. 1 of a device in process of manufacture.

Here, compound semiconductor layers made of GaAs over the substrate 10 are formed by MOCVD (Metal Organic Chemical Vapor Deposition) method, for example. As a raw material of Group III-V compound semiconductor, for example, trimethyl aluminum (TMA), trimethyl gallium (TMG), trimethyl indium (TMIn), and arsine (AsH₃) are used. As a raw material of a donor impurity, for example, H₂Se is used. As a raw material of an acceptor impurity, for example, dimethyl zinc (DMZ) is used.

First, the lower DBR layer 11, the lower spacer layer 12, the active layer 13, the upper spacer layer 14, the oxidized layer 15D, the upper DBR layer 16, and the contact layer 17 are layered over the substrate 10 in this order. After that, a resist layer R1 is formed on the contact layer 17 (FIG. 6A).

Next, the contact layer 17, the upper DBR layer 16, the oxidized layer 15D, the upper spacer layer 14, the active layer 13, the lower spacer layer 12, and the upper part of the lower DBR layer 11 are selectively etched by, for example, RIE (Reactive Ion Etching) method to form the mesa 18 (FIG. 6B).

Next, oxidation treatment is performed at high temperature in the water vapor atmosphere to selectively oxidize Al of the oxidized layer 15D from the side face of the mesa 18. Thereby, the peripheral region of the oxidized layer 15D becomes an insulating layer (aluminum oxide). That is, the peripheral region becomes the current confinement region 15A, and only the central region becomes the current injection region 15B. Accordingly, the current confinement layer 15 is formed (FIG. 7A). After that, the resist layer R1 is removed.

Next, a resist layer R2 is formed on the top of the mesa 18. After that, the central part of the contact layer 17 is selectively removed by, for example, wet etching to form an aperture (FIG. 7B). After that, the resist layer R2 is removed.

Next, the foregoing dielectric material is deposited on the entire surface including the surface of the mesa 18 by, for example, CVD (Chemical Vapor Deposition) method. After that, the deposited dielectric material is selectively removed by etching so that the portion corresponding to the region other than the specific region 23E is left in the top face of the mesa 18. Thereby, the first adjustment layer 23A is formed (FIG. 8A).

Next, by using the method similar to the foregoing method, the second adjustment layer 23B is formed on the first adjustment layer 23A. After that, the third adjustment layer 23C is formed in the specific region 23E of the top face of the mesa 18. Further, the protective film 20 is formed on the side face of the mesa 18 and the surface on the periphery of the mesa 18 (FIG. 8B). The foregoing dielectric material has superior selectivity for semiconductors such as the upper DBR layer 16. Further, the foregoing dielectric material does not need to be formed in a complicated shape. Therefore, the first adjustment layer 23A is able to be easily formed by etching.

In the case where the second adjustment layer 23B, the third adjustment layer 23C, and the protective film 20 have the same film thickness and are made of the same material, these layers are preferably formed collectively in order to simplify the manufacturing process.

Next, the foregoing metal material is layered on the entire surface by, for example, vacuum evaporation method. After that, for example, by selective etching of the metal layer, the upper electrode 19 having an aperture in the central region of the top face of the mesa 18 is formed, and the electrode pad 21 is formed on the surface on the periphery of the mesa 18.

Next, the rear face of the substrate 10 is polished as appropriate and the thickness thereof is adjusted. After that, the lower electrode 22 is formed on the rear face of the substrate 10. Consequently, the laser diode 1 of this embodiment is manufactured.

Next, a description will be given of operation and effect of the laser diode 1.

In the laser diode 1, when a given voltage is applied between the upper electrode 19 and the lower electrode 22, a current is injected into the active layer 13 through the current injection region 15B of the current confinement layer 15. Thereby, light is emitted due to electron-hole recombination. Such light is reflected by the pair of the lower DBR layer 11 and the upper DBR layer 16. Laser oscillation is generated at a given wavelength λ. Then, the light is emitted as a laser beam outside.

In general, in the VCSEL, there is a tendency that light output of the fundamental transverse mode is largest in the central part of the light emitting aperture, and is decreased with distance from the opposed region opposing to the center point of the current injection region. Therefore, in the case where the VCSEL is used for high output purposes, it is preferable that the aperture (light emitting window) of the upper electrode is large enough to extract laser light of the fundamental transverse mode as much as possible. However, in general, there is a tendency that light output of the high-order transverse mode is largest in a region away from the center point of the current injection region at a certain distance, and is decreased with distance from such a region toward the center point of the current injection region Thus, in the case where the light emitting window is excessively large, the laser light of the high-order transverse mode may be also outputted on high output.

Therefore, in the VCSEL of related art, the laser light of the high-order transverse mode is prevented from being emitted by the following measures. That is, the size of the current injection region is decreased. Otherwise, a reflectance adjustment layer is provided in the central part of the light emitting window, and thereby a region where the fundamental transverse mode is mainly shown is set to a region with high reflectance, and a region where high-order transverse mode is mainly shown is set to a region with low reflectance.

For example, as illustrated in FIGS. 9A and 9B, in the case where the laminated structure 23D is arranged so that the center point C2 of the laminated structure 23D corresponds to the opposed region C1 opposing to the center point of the current injection region 15B, as illustrated in α1 and β1 of FIG. 10, the smaller the width (diameter) W₁ of the laminated structure 23D is, the larger the difference between mirror loss of 0 order transverse mode and mirror loss of primary order transverse mode is. However, in the case where the width W₁ of the laminated structure 23D is small (for example, 3.2 μm), the light output is lower than 90% of the light output in the case where the transverse mode adjustment section 23 is not provided on the upper DBR layer 16. Meanwhile, however, in the case where the width W₁ of the laminated structure 23D is large (for example, 4.5 μm), the light output exceeds 90% of the light output in the case where the transverse mode adjustment section 23 is not provided on the upper DBR layer 16, but the difference between the mirror loss of the 0 order transverse mode and the mirror loss of the primary order transverse mode becomes extremely small, and it is difficult to obtain gain of the high-order transverse mode that is extremely smaller than gain of the fundamental transverse mode. As a result, high-order transverse mode oscillation is generated, and NFP (Near Field Pattern) is distorted. As described above, in the existing method, light output and NFP are in relation of trade-off.

Meanwhile, in this embodiment, the laminated structure 23D is provided in the region other than the specific region 23E in the top face of the mesa 18, and the third adjustment layer 23C is provided in the region including the specific region 23E. Thereby, as illustrated in FIG. 5B, the reflectance in the third adjustment layer 23C (high reflectance area) is lower than the reflectance in the laminated structure 23D (low reflectance area). Thus, in the foregoing primary mode including the four peaks P of double rotation symmetry or quad rotation symmetry, at least one gain out of a pair of peaks opposing with the opposed region C1 in between is inhibited. The foregoing primary mode is a mode in which two sets of a pair of peaks opposing with the opposed region C1 in between are overlapped. Therefore, by suppressing at least one gain out of the two peaks respectively included in each set, gains of each set are able to be suppressed.

For example, in the case where the laminated structure 23D is arranged in the region other than the specific region 23E, and the center point C2 of the laminated structure 23D is deviated from the opposed region C1 by about 1 μm, as shown in α2 and β2 of FIG. 10, not only in the case where the width W₁ of the laminated structure 23D is small (for example, 3.2 μm) but also in the case where the width W₁ of the laminated structure 23D is large (for example, 4.5 μm), the difference between the mirror loss of the 0 order transverse mode and the mirror loss of the primary order transverse mode is able to be increased. That is, only by deviating the center point C2 of the laminated structure 23D from the opposed region C1, the difference between the mirror loss of the 0 order transverse mode and the mirror loss of the primary order transverse mode is able to be increased. Thereby, it is possible to obtain gain of the high-order transverse mode that is extremely smaller than gain of the fundamental transverse mode. Thus, high-order transverse mode oscillation is able to be prevented, and NFP is able to be in the shape of a top hat. The light output in the case where the width W₁ of the laminated structure 23D is large (for example, 4.5 μm) exceeds 90% of the light output in the case where the transverse mode adjustment section 23 is not provided on the upper DBR layer 16. Therefore, it is found that by setting the width W₁ of the laminated structure 23D to an appropriate size, it is possible to obtain high output of the high-order transverse mode while suppressing the high-order transverse mode oscillation. That is, in this embodiment, both light output and NFP are able to be satisfied.

The foregoing mirror loss is defined individually and respectively for the fundamental transverse mode and the primary transverse mode. Specifically, where a volume in a portion where a high reflectance area of the transverse mode adjustment section 23 (laminated structure 23D) and the fundamental transverse mode are overlapped is V_{o (high)}, a volume in a portion where the high reflectance area of the transverse mode adjustment section 23 (laminated structure 23D) and the primary mode are overlapped is V_{1 (high)}, a volume in a portion a high reflectance area of the transverse mode adjustment section 23 (laminated structure 23D) and the fundamental transverse mode are not overlapped is V_{o (low)}, and a volume in a portion where the high reflectance area of the transverse mode adjustment section 23 (laminated structure 23D) and the primary mode are not overlapped is V_{1 (low)}, mirror loss _{αM (high)} of the high reflectance area (laminated structure 23D) and mirror loss _{αM (low)} of a low reflectance area (portion other than the laminated structure 23D of the transverse mode adjustment section 23) are derived from Febry-Perot model as shown in the following Mathematical formulas 1 and 2. V_{o (high)} and V_{1 (low)} are normalized for every mode as shown in the following Formulas 4 and 5.

$\begin{array}{cc}{\alpha }_{M\left(\mathrm{high}\right)}=\frac{1}{2L}·L_n\left[\frac{1}{\sqrt{R_{t\left(\mathrm{high}\right)}·R_b}}\right]& \mathrm{Mathmatical}\mathrm{formula}1\\ {\alpha }_{M\left(\mathrm{low}\right)}=\frac{1}{2L}·L_n\left[\frac{1}{\sqrt{R_{t\left(\mathrm{low}\right)}·R_b}}\right]& \mathrm{Mathmatical}\mathrm{formula}2\\ V_{0\left(\mathrm{high}\right)}+V_{0\left(\mathrm{low}\right)}=1& \mathrm{Formula}4\\ V_{1\left(\mathrm{high}\right)}+V_{1\left(\mathrm{low}\right)}=1& \mathrm{Formula}5\end{array}$

Rb in Mathematical formulas 1 and 2 represents reflectance of the lower DBR layer 11. R_{t (high)} represents reflectance of a high reflectance area of the upper DBR layer 16. R_{t (low)} represents reflectance of a low reflectance area of the upper DBR layer 16. It is needless to say that, due to reflectance relation, _{αM (high)} is smaller than _{αM (low)}.

Accordingly, mirror loss _α⁰_M of the fundamental transverse mode and mirror loss _α¹_M of the primary transverse mode are as shown in the following Mathematical formula 3. As understood from Mathematical formula 3, in the case where the high reflectance area becomes larger, V_{o (high)} and V_{1 (high)} become larger and V_{0 (low)} and V_{1 (low)} become smaller. Therefore, _α⁰_M and _α¹_M become smaller, and finally become equal to _{αM (high)}.

$\begin{array}{cc}\frac{1}{{\alpha }_m^M}=\frac{V_{m\left(\mathrm{high}\right)}}{{\alpha }_{M\left(\mathrm{high}\right)}}+\frac{V_{m\left(\mathrm{low}\right)}}{{\alpha }_{M\left(\mathrm{low}\right)}}& \mathrm{Mathmatical}\mathrm{formula}3\\ \left(m=0,1\right)& \end{array}$

Further, in this embodiment, even in the case where the center point C2 of the laminated structure 23D is deviated from the opposed region C1, or in the case where the shape of the laminated structure 23D is a shape other than a circle (for example, in the shape of a convex or a cross), the center position of NFP corresponds with the center point C1 of the current injection region 15B, and NFP becomes circular irrespective of the shape of the laminated structure 23D. Therefore, there is no possibility that the general versatility of the laser diode 1 is lowered.

Further, in this embodiment, as described above, it is extremely easy to selectively etch the first adjustment layer 23A, and it is not necessary to form the first adjustment layer 23A, the second adjustment layer 23B, and the third adjustment layer 23C in a complicated shape. Therefore, the laser diode 1 is easily manufactured.

Further, in this embodiment, it is not necessary to use a special substrate, and it is not necessary to provide a component with a complicated shape and a complicated structure in the aperture of the upper electrode 19. Thus, the laser diode 1 is able to be easily and inexpensively manufactured. Further, it is not necessary to decrease the size of the mesa 18. Thus, it is possible to secure a large area of the current injection region 15B and the aperture of the upper electrode 19, and it is possible to obtain low resistance of the semiconductor layer 30 (resonator) and high output of the laser light. Therefore, a practical VCSEL is obtainable.

MODIFIED EXAMPLES

In the foregoing embodiment, the laminated structure 23D is circular. However, for example, as illustrated in FIGS. 11A to 11C, the laminated structure 23D may be in the shape of a convex protruding toward a region sandwiched between the specific regions 23E. Otherwise, for example, as illustrated in FIGS. 12A to 12C, the laminated structure 23D may be in the shape having double convexes protruding toward two regions sandwiched between the specific regions 23E. Further, for example, as illustrated in FIGS. 13A to 13C, the laminated structure 23D may be in the shape of a cross in the region other than the region corresponding to each peak P of the opposed region opposing to the current injection region 15B.

For example, if the laminated structure 23D is circular, and the laminated structure 23D is arranged so that the center point C2 of the laminated structure 23D corresponds to the opposed region C1, as illustrated in FIG. 14, output of a simple transverse mode is able to be largest in the case where the width W₁ of the laminated structure 23D is about 3.65 μm. However, even in this case, the light output is about 90% of the light output in the case where the transverse mode adjustment section 23 is not provided on the upper DBR layer 16.

Meanwhile, for example, as illustrated in FIGS. 11A to 11C, in the case where the laminated structure 23D is in the shape of a convex and the width W₁ of the laminated structure 23D is about 3.0 μm, as illustrated in FIG. 14, the difference between the mirror loss of the 0 order transverse mode and the mirror loss of the primary transverse mode is able to be increased while the magnitude of mirror loss of the primary transverse mode is almost equal to that in the case where the laminated structure 23D is circular. Thereby, the gain of the high-order transverse mode is able to be extremely smaller than the gain of the fundamental transverse mode. Thus, the high-order transverse mode oscillation is able to be prevented, and NFP is able to be in the shape of a top hat. Further, compared to the case that the laminated structure 23D is circular, the light output is able to be increased up to about 96%.

Further, for example, as illustrated in FIGS. 13A to 13C, in the case where the laminated structure 23D is in the shape of a cross and the width W₁ of the laminated structure 23D is about 3.5 μm, as illustrated in FIG. 14, the difference between the mirror loss of the 0 order transverse mode and the mirror loss of the primary transverse mode is able to be large while the magnitude of mirror loss of the primary transverse mode is almost equal to that in the case where the laminated structure 23D is circular. Thereby, the gain of the high-order transverse mode is able to be extremely smaller than the gain of the fundamental transverse mode. Thus, the high-order transverse mode oscillation is able to be prevented, and NFP is able to be in the shape of a top hat. Further, compared to the case that the laminated structure 23D is circular, the light output is able to be increased up to about 94%.

As described above, in the foregoing each modified example, the output of the fundamental transverse mode is able to be further increased, while oscillation of the high-order transverse mode is prevented.

In FIGS. 11A to 11C, FIGS. 12A to 12C, and FIGS. 13A to 13C, the width W₁ of the laminated structure 23D is a value twice the distance between the portion closest to the center point C1 of the current injection region 15B in the outer rim of the laminated structure 23D and the center point C1 of the current injection region 15B.

Descriptions have been hereinbefore given of the invention with reference to the embodiment and the modified examples. However, the invention is not limited to the foregoing embodiment and the like, and various modifications may be made.

For example, in the foregoing embodiment, the transverse mode adjustment section is composed of the first adjustment layer 23A, the second adjustment layer 23B, and the third adjustment layer 23C. However, the transverse mode adjustment section may have other structure. In short, any structure may be adopted as long as in the foregoing primary mode including the four peaks P of double rotation symmetry or quad rotation symmetry, at least one gain of a pair of peaks opposing with the opposed region C1 in between is prevented.

Further, in the foregoing embodiment and the like, the invention has been described with reference to the AlGaAs-based compound laser diode as an example. However, the invention is also applicable to other compound laser diodes such as a GaInP-based laser diode, an AlGaInP-based laser diode, an InGaAs-based laser diode, a GaInP-based laser diode, an InP-based laser diode, a GaN-based laser diode, a GaInN-based laser diode, and a GaInNAs-based laser diode.

It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alternations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

Claims

1. A Vertical cavity surface emitting laser comprising:

a semiconductor layer including an active layer and a current confinement layer; and

a transverse mode adjustment section formed on the semiconductor layer,

wherein the current confinement layer has a current injection region and a current confinement region,

the transverse mode adjustment section has a high reflectance area and a low reflectance area,

the high reflectance area is formed in a region including a first opposed region opposing to a center point of the current injection region,

a center point of the high reflectance area is arranged in a region different from the first opposed region, and

the low reflectance area is formed in a region where the high reflectance area is not formed, in an opposed region opposing to the current injection region.

2. The Vertical cavity surface emitting laser according to claim 1,

wherein the high reflectance area is formed in a region other than a specific region in an opposed region opposing to a region generating a high order transverse mode including four peaks of double rotation symmetry or quad rotation symmetry, and

the specific region is a region corresponding to two peaks facing each other with a region other than the first opposed region in between.

3. The Vertical cavity surface emitting laser according to claim 1, wherein a distance between the center point of the high reflectance area and the center point of the current injection region is 10% or more of a diameter of the current injection region.

4. The Vertical cavity surface emitting laser according to claim 1, wherein a diameter of the high reflectance area is 60% or more of a diameter of the current injection region.

5. The Vertical cavity surface emitting laser according to claim 1, wherein the high reflectance area is in the shape of a convex protruding toward a region sandwiched between the specific regions.

6. The Vertical cavity surface emitting laser according to claim 1,

wherein the semiconductor layer includes a first multilayer film reflector formed on an opposite side to the transverse mode adjustment layer in relation to the active layer, and a second multilayer film reflector formed on the transverse mode adjustment layer side in relation to the active layer,

the high reflectance area has a structure obtained by layering a first adjustment layer and a second adjustment layer in this order, the first adjustment layer having a film thickness of (2a−1)λ/4n₁ (a is an integer number of 1 or more, λ is a light emitting wavelength, and n₁ is a refractive index) and the refractive index n₁ lower than that of a surface of the second multilayer film reflector, the second adjustment layer having a film thickness of (2b−1)λ/4n₂ (b is an integer number of 1 or more, and n₂ is a refractive index) and the refractive index n₂ higher than that of the first adjustment layer, and

the low reflectance area is a third adjustment layer having a film thickness of (2c−1)λ/4n₃ (c is an integer number of 1 or more, and n₃ is a refractive index) and the refractive index n₃ higher than that of the first adjustment layer.

7. The Vertical cavity surface emitting laser according to claim 6, wherein the first adjustment layer and the second adjustment layer are made of a dielectric material different from each other.

8. The Vertical cavity surface emitting laser according to claim 7,

wherein the first adjustment layer is composed of an oxide, and

the second adjustment layer and the third adjustment layer are composed of a nitride.

9. A semiconductor laser comprising:

a semiconductor layer including an active layer and a current confinement layer, the current confinement layer including a current injection region; and

a transverse mode adjustment section formed on the semiconductor layer, the transverse mode adjustment section including a high reflectance area and a low reflectance area,

wherein a center point of the high reflectance area is offset from a center point of the current injection region.

10. The semiconductor laser according to claim 9,

wherein the low reflectance area is formed in a region where the high reflectance area is not formed.

11. The semiconductor laser according to claim 9,

wherein the high reflectance area is formed in a region other than a specific region in an opposed region opposing to a region generating a high order transverse mode including four peaks of double rotation symmetry or quad rotation symmetry, the specific region being a region corresponding to two peaks facing each other with a region other than the first opposed region in between.

12. The semiconductor laser according to claim 9,

wherein the center point of the high reflectance area is offset from the center point of the current injection region by a distance that is 10% or more of a diameter of the current injection region.

13. The semiconductor laser according to claim 9,

wherein a diameter of the high reflectance area is 60% or more of a diameter of the current injection region.

14. The semiconductor laser according to claim 9,

wherein the high reflectance area is in the shape of a convex protruding toward a region sandwiched between the specific regions.

15. The semiconductor laser according to claim 9,

wherein the active layer is formed between a first multilayer film reflector and a second multilayer film reflector, the second multilayer film reflector being closer to the transverse mode adjustment layer than the first multilayer film reflector.

16. The semiconductor laser according to claim 15,

wherein the high reflectance includes a first adjustment layer and a second adjustment layer, the first adjustment layer having a film thickness of (2a−1)λ/4n₁ (where a is an integer number of 1 or more, λ is a light emitting wavelength, and n₁ is a refractive index) and the refractive index n₁ is lower than a refractive index of a surface of the second multilayer film reflector, the second adjustment layer having a film thickness of (2b−1)λ/4n₂ (where b is an integer number of 1 or more, and n₂ is a refractive index) and the refractive index n₂ is higher than the refractive index of the first adjustment layer, and

the low reflectance area includes a third adjustment layer having a film thickness of (2c−1)λ/4n₃ (where c is an integer number of 1 or more, and n₃ is a refractive index) and the refractive index n₃ is higher than the refractive index of the first adjustment layer.

17. The Vertical cavity surface emitting laser according to claim 16, wherein the first adjustment layer and the second adjustment layer are made of a dielectric material different from each other.

18. The Vertical cavity surface emitting laser according to claim 17,

wherein the first adjustment layer is composed of an oxide, and

the second adjustment layer and the third adjustment layer are composed of a nitride.

19. A Vertical cavity surface emitting laser comprising:

a semiconductor layer including a first multilayer film reflector, an active layer, a current confinement layer and a second multilayer film reflector formed in this order, the current confinement layer including a current injection region; and

a transverse mode adjustment section formed on the semiconductor layer, the transverse mode adjustment section including a high reflectance area and a low reflectance area,

wherein, in a plan view, a center point of the high reflectance area is offset from a center point of the current injection region.

20. The Vertical cavity surface emitting laser according to claim 19, further comprising a first dielectric layer made of a first dielectric material, the first dielectric layer being disposed within the high reflectance area.

21. The Vertical cavity surface emitting laser according to claim 20, further comprising a second dielectric layer made of a second dielectric material different from the first dielectric material, the second dielectric layer being disposed in an area outside of the high reflectance area.

22. The Vertical cavity surface emitting laser according to claim 21, wherein the low reflectance area is located in the area outside of the high reflectance area.

23. The Vertical cavity surface emitting laser according to claim 21, wherein the first dielectric material includes silicon dioxide, and the second dielectric material includes silicon nitride.

24. The Vertical cavity surface emitting laser according to claim 21, further comprising a protective film,

wherein a portion of the semiconductor layer has a mesa structure, and the protective film is disposed on a side wall of the mesa structure.

25. The Vertical cavity surface emitting laser according to claim 24, wherein the protective film is made of the second dielectric material.

26. The Vertical cavity surface emitting laser according to claim 20, wherein the first dielectric layer has a circular shape.

27. The Vertical cavity surface emitting laser according to claim 26, wherein, in the plan view, a center point of the circular shape is offset from the center point of the current injection region.

28. The Vertical cavity surface emitting laser according to claim 26, wherein, in the plan view, the current confinement layer further includes a current confinement region that overlaps with the first dielectric layer.